ANATOMY AND OLASSTFIOATION OP THE ARENIOOLID^. 537 



ingly Mesnil has included Branchiomaldane as a second 

 genus of the family Arenicolidae. Further distinctive features 

 are derived from the nephridia, the absence of otocysts, and 

 esj)eciall3^ the sexual maturity of these hermaphrodite worms. 

 One or two of the early developmental stages are roughly 

 figured by Mesnil. 



Before accepting this conclusion we may be permitted to 

 add some observations made on the specimens with which 

 M. Mesnil kindly supplied us. We have only been able to 

 find in a specimen 11 millimetres iong^ which we cut into 

 transverse sections, two pairs of ducts openiug on the fifth and 

 sixth chfetigerous annuli. Moreover very distinct apertures 

 in these segments occur in all our specimens, but Mesnil (1898) 

 describes a specimen 15 mm. long, " les organes segmentaires 

 plus ou moins pigmentes de noir dans les somites 7, 8, 9, 10." 

 In the later paper he states, ''II n'y a que quatre ou cinq 

 paires de nephridies." The two pairs of tubes in our sections 

 have no funnel, and resemble the nephridia of a post-larval 

 Arenicola in structure and relations. They contain gonads, 

 and apparently function as ducts. More recently Fauvel 

 (1899) has stated that there are three to five pairs of ne- 

 phridia in segments 5 — 9. 



A point in which this Branchiomaldane differs very 

 widely from Arenicola is the mode of origin of the gonads. 

 Both ovaries and testes are found in the lateral section of the 

 coelom in the tail region. They certainly are not confined to 

 the nephridia or the nephridial region, unless there be a large 

 number of larval nephridia which disappear at a very early 

 stage. The absence of the otocysts we have confirmed. The 

 gills are outgrowths of the body-wall, with coelomic cavities 

 containing afferent and efferent blood-vessels. 



On the external characters alone there is little to be said 

 against including Branchiomaldane in the family Areni- 

 colidffi. The question is whether the absence of otocysts, 

 the hermaphrodite character and peculiar mode of origin of 

 the gonads taken together form a stronger claim for affinity 

 to Arenicolidae or to the Maldanidae. Now one species 



